Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a set of air interface specifications in wireless local area network developed for Dedicated Short Range Communication (DSRC) by IEEE Committee, which provides wireless network service based on a competition scheme. In IEEE 802.11 wireless network, before transmitting a data packet, a station (STA) or an access point (AP) needs to monitor a channel to determine whether the channel is clear, and if yes, experience a random back-off process. Or else, the STA or AP cannot transmit the data packet and needs to monitor the channel again. Sometimes, when the channel is determined to be clear, data packets are transmitted. However, there is a chance that some data packets which are actually being transmitted in the particular channel may be mis-detected or not be detected because another STA or AP which is transmitting these data packets is far away and has a low power. That is to say, the channel, which is determined to be clear by the particular STA or AP, is actually noisy. As a result, inter-frame collision may occur among the data packets transmitted by multiple STAs or APs, which causes invalid packet transmission.
A packet aggregation function has been involved in IEEE 802.11n and IEEE802.11ac, which enables a lengthened aggregation frame formed by a plurality of aggregation sub-frames to be transmitted in a channel.
For example, an aggregation-media access control service data unit (A-MSDU) frame aggregates multiple media access control service data units (MSDUs). These MSDUs share the same media access control (MAC) frame head and the same frame check sequence (FCS). The FCS is used in a check process. As the aggregation frame has one unified FCS, once an error in the transmission of any one of the MSDUs occurs, reception of the whole A-MSDU frame at a receiver will be invalid, and then the receiver may require the SAT or AP to retransmit the A-MSDU frame. For an aggregation-media access control protocol data unit (A-MPDU) frame, it aggregates multiple media access control protocol data units (MPDUs). Each MPDU in the A-MPDU frame has an independent FCS. When a FCS collides with a frame head of a physical layer protocol data unit (PPDU) which corresponds to the A-MPDU, the reception of the A-MPDU may fail.
The packet aggregation function can improve data packet transmission ability in a wireless local area network and a throughput rate of a channel. In an aggregation frame, the more sub-frames are aggregated, the longer the aggregation frame to be transmitted becomes. However, the wireless transmission environment is generally complicated, thus the length of an aggregation frame needs to be carefully configured to reduce the possibility of inter-frame collision and interference among different STAs or APs in a wireless channel.